Friday, 11 June 2010

T 360/07 – Striving For Purity

[3.2] Document D3 discloses […] the production of amorphous (S)-omeprazole magnesium salt by dissolving (S)-omeprazole magnesium salt in ethanol and introducing the solution into CO2 as an antisolvent.

[3.3] Whereas claim 4 of the main request requires that the magnesium omeprazole has “a residual organic solvent content of less than 7% by weight”, document D3 does not specify the organic solvent content of the products disclosed therein. Therefore, it is to be assessed whether or not this feature of claim 4 renders its subject-matter novel.

[3.4] The [patent proprietor] considered decision T 142/06 to apply to this case rather than T 990/96 […].

[3.4.1] Decision T 990/96 [7] states that
“... a document disclosing a low molecular chemical compound and its manufacture makes available this compound to the public in the sense of Article 54 EPC in all grades of purity as desired by a person skilled in the art” if “Conventional methods for the purification ... such as recrystallisation, distillation, chromatography, etc., which normally can be successfully applied in purification steps, are within the common general knowledge of those skilled in the art.”
This statement is preceded by the following:
“It is common general knowledge that any chemical compound obtained by a chemical reaction will normally contain impurities for various reasons, such as sidereactions, incomplete conversion of starting materials, etc., and that it is not possible for thermodynamical reasons to obtain a compound, which is - in the strict sense - completely pure, i.e. totally free of any impurity.” (see point [6] of the reasons).
This clearly indicates that the conclusion drawn in point [7] of the reasons for the decision not only applies to the type of impurity of the specific case (here the threo isomer in the respective erythro isomer) but to impurities in general, namely to any undesired compound present in the desired product.

[3.4.2] The [patent proprietor] considered residual solvent not to be an impurity. It referred to US patent D20 which defines that “references herein to ‘impurities’ are to be understood as not including residual solvents ...” […]. However, the word “herein” in this citation indicates that said definition was made only for the purpose of this document, possibly in contrast to the general meaning of the term “impurity”.

Magnesium omeprazole is used as an active agent in pharmaceutical compositions (see document (D7) […]). High contents of organic solvents in general are undesirable and even moderate contents of methanol (the most preferred solvent according to the patent in suit) inacceptable in pharmaceutical compositions (see document D22 […]). Consequently, residual organic solvents in general and methanol in particular are to be regarded as impurities whenever present in magnesium omeprazole. Hence, the decision T 990/96 might be relevant for the present case.

[3.4.3] Decision T 142/06 [3.27-3.3.2] refers to T 990/96. Under point [3.29] of the reasons it bases its deviation from T 990/96 on the fact that only the low content of chlorine in the latex enables the production of films of the desired oxygen barrier and boil blushing properties. The present case differs from the one of T 142/06 in that here the desired therapeutical effect is only based on magnesium omeprazole as such. Therefore, the reasons to deviate from T 990/96 indicated in T 142/06 do not apply to the present case. Consequently, there is no reason to apply the conclusions drawn in T 142/06 to the present case.

[3.4.4] Decision T 990/96 [7] states that the absence of impurities cannot contribute to novelty only if said purification can be achieved by conventional means. Such conventional means include the evaporation of the solvent as suggested in example 6 of document D7. Furthermore, detailed methods for the effective removal of residual solvents by drying were known from the review article D22 […].

[3.4.5] Consequently, there is no reason to deviate from the decision T 990/96. All the features of claim 4 are explicitly disclosed in […] D3 except the requirement that the residual organic solvent content has to be less than 7% by weight. As this range for the organic solvent content cannot contribute to novelty, the subject-matter of claim 4 of the Main Request lacks novelty under A 54(3) […].

To read the whole decision, click here.